This disclosure relates to a method and apparatus for correcting abnormal flexion of the joints of the human foot. More particularly, this disclosure relates to a combination of dorsifexion of the metatarsal/proximal phalangeal joint and plantar flexion of the proximal interphalangeal joint, commonly called a hammer toe.
The lesser toes of the human foot are composed of three bones and contain two joints. The three toe bones are a proximal phalanx (closest to the metatarsal bone), a middle phalanx, and a distal phalanx (at the end of the toe). The three toe bones are connected by two toe joints, a proximal interphalangeal joint (PIPJ), which is formed by a distal end of the proximal phalanx and a proximal portion of the middle phalanx; and a distal interphalangeal joint (DIPJ), distal to the PIPJ and formed by a distal end of the middle phalanx and a proximal end of the distal phalanx.
Contraction of the lesser toes of the foot is a common pathologic condition due to an imbalance between the tendons on the top and bottom of the toe(s). When an affected toe is able to be straightened out manually, i.e. by an individual or an eternal force, it is referred to as a flexible hammer toe. If left untreated these flexible contractures will become a fixed deformity know as a rigid hammer toe, which cannot be put back into normal alignment. The PIPJ is more implicated in a hammer toe syndrome deformity then the DIPJ.
There are many palliative modalities such as pads and various forms of orthodigital devices used to accommodate toe deformities. Those conservative options, however, do not provide an individual with enough comfort and in some cases are simply illogical given the fact that various alternative surgical options are available.
Throughout the history of performing toe surgery many methods have been attempted by surgeons ranging from simple tendon release, partial joint excision, full joint excision and, as a final resort, complete fusion (arthrodesis) of a joint rendering a straight toe. Arthrodesis of the joint is usually reserved for severe deformities or in cases where previous non-arthrodesic procedures were performed but failed to provide a patient with desired expectations.
In the past some surgeons fused the PIPJ joint by a simple end-to-end method. In this procedure a surgeon resects the articular cartilage of the end of one toe bone and the base of an adjoining bone which forms an abnormal joint. The two ends are approximated to each other with the expectation that they will fuse together. An inherent problem with this method is a high rate of non-union with possible recurrence of deformity.
Another method is to insert a smooth pin or wire that extends out of the distal end of the toe. The wire is used to hold the ends of the bones in alignment until fusion occurs. Because these wires and pins are smooth, however, it is possible for the joint to distract leading to a failure or non-union.
Additionally, yet another method was developed which utilized a thin screw inserted from the tip of a toe across the joint. The purpose of this device was to provide compression which facilitates end-to-end fusion. The insertion of a specialized screw is difficult to perform and presents a possibility of damaging the DIPJ. Furthermore, when the pin is removed it requires a second surgical procedure.
Yet, another device was developed utilizing “memory” metal that was simply inserted into either the DIPJ or PIPJ after resection of the joint. These devices are relatively expensive when compared to pins, wires, or screws and also have been known to sometimes expand too quickly rending the device ineffective.
Finally, a hinged toe fusion device was developed to replace the PIPJ. Each end of the device was inserted into a corresponding end of the bones flanking the PIPJ. A limitation with this device is that it is relatively difficult to work with. The two components are not designed to be easily separated. Also, the device can be difficult to properly align and can rotate out of the proper position after insertion. Also, it does not allow for the additional use of a pin or wire to be inserted across the metatarsophalangeal joint (MPJ), the joint proximal to the PIPJ, which is sometimes desirable.
The difficulties and limitations suggested in the preceding are not intended to be exhaustive, but rather are among many which demonstrate that although significant attention has been devoted to surgically correcting hammer toe disfigurement, nevertheless surgical implants and procedures appearing in the past will admit to worthwhile improvement.